Polymeric storage bags are well known in the art and are commonplace in the market. Consumers use these bags for storage of a multitude of materials and purposes. More recently, polymeric storage bags with mechanical closure systems have become commonplace as well. The closure systems are integrated into the bag and offer great convenience over traditional bags that must be closed with a separate closure device, such as a thin, twistable metal wire or other fitting designed to be placed around the orifice-end of the bag. Although these bags are of great utility, they have a variety of limitations and disadvantages. For example, the closure systems tend to leak, particularly at the sides of the bag. Also, bags typically offer little or no structural integrity to liquid materials and therefore are not ideal storage devices for such materials. It can be difficult to utilize bags as a dispensing device, such as a serving container for foods, since sidewalls have little structural integrity and therefore can be difficult to maintain in a fully open configuration.
Rigid containers are also well known in the art. They offer many advantages over bags due to their rigid shape, such as ability to store liquids and to remain in a fully open configuration. However they suffer from a different set of drawbacks. For example they can be cumbersome to store and tend to be more expensive to manufacture than bags. Inexpensive rigid containers can be made, however these still suffer from the same storage disadvantage and further, tend to have poor quality seals, such that liquid materials contained in the container can leak.
It is also known to combine the benefits of bags and rigid containers in a single device while avoiding the disadvantages of both. More particularly, collapsible containers have been disclosed that can be conveniently stored in a flat configuration when not in use, but can be expanded into a rigid or semi-rigid container prior to use. For example, U.S. Pat. No. 5,179,897, issued Jan. 10, 1995 to Muckenfuhs et al. (The Procter & Gamble Company), incorporated herein by reference, discloses such a resiliently deformable container which can be stored in a flattened position when not in use, but which can be expanded to a three dimensional shape suitable for containing materials whenever desired. U.S. Pat. No. 5,996,882, issued Dec. 7, 1999 to Randall (The Procter & Gamble Company) discloses a reversibly collapsible container wherein the sidewalls can be articulated about two spaced apart lines of weakness that facilitate easy folding of the sidewalls for collapsing and expanding of the container.
U.S. Pat. No. 4,694,986, issued Sep. 22, 1987 to Chou, discloses another form of a container having fold lines. U.S. Pat. No. 4,678,095, issued Jul. 7, 1987 to Barnett et al., discloses a polygonal collapsible container. U.S. Pat. No. 5,575,398, issued Nov. 19, 1996 to Robbins III, discloses a collapsible container having axially movable sidewalls. U.S. Pat. No. 5,524,789, issued Jun. 11, 1996 to Jackman, discloses a container that is collapsible upon rotation between the top and bottom of the container. U.S. Pat. No. 3,949,933, issued Apr. 13, 1976 to Giambrone et al., discloses a collapsible container having sidewall panels that separate from adjacent sidewall panels upon collapse. U.S. Pat. No. 4,930,644, issued Jun. 5, 1990 to Robbins, III, teaches a collapsible thin film plastic container which does not have hinge lines in the sidewall.
U.S. Pat. No. 3,319,684, issued May 16, 1967 to Calhoun, discloses a container having ends with diagonal fold lines longer than the straight line distance between opposite ends of the fold lines. U.S. Pat. No. 3,197,062, issued Jul. 27, 1965 to Day et al., discloses an accordion-type tissue dispensing carton having both sidewalls and end walls which are hinged inwardly.
Despite these patents, it remains desirable to further improve the art in the area of reversibly collapsible containers. For example, it is desirable to provide reversibly collapsible containers that can be folded and expanded without the occurrence of fold lines or crease lines in the vicinity of the axis upon which the walls of the container are folded. Fold or crease lines induced as a result of irreversible stresses occurring within folded walls and typically appear as white lines running coextensively with the fold. In addition to an unsightly appearance, fold or crease lines can lead to structural flaws in the wall, ultimately resulting in leakage into or out from the container.
It is also desirable to provide reversibly collapsible containers which contain an integrated closure system which provides sufficient structural integrity for leak-free performance, yet which retains light, flexible walls for easy folding to an essentially flat configuration for storage or disposal.
It is further desirable to provide reversibly collapsible containers that are made from a clear or translucent polymer, such that materials being stored in the container can be seen without opening the container or emptying its contents.
It is still further desirable to provide reversibly collapsible containers that are heat resistant, so that for example) contents being stored in the container can be heated (e.g., food items), and that materials being stored in the container upon exposure to heat (whether intentional or incidental) are not damaged or contaminated by the polymer utilized constructing the container. It is especially desirable to provide a reversibly collapsible container as above made from a food-grade plastic, and further, a material that is suitable for cooking or heating, such as but not limited to microwaving and submersion in hot water.
Yet another desirable parameter of a reversibly collapsible container is that it be resistant to cracking at low temperatures. Such "cold cracking resistance" is particularly desirable to be provided in a container with collapsible sidewalls which is also heat resistant (and preferably microwavable), so that a container containing a material (such as but not limited to food) can be stored in a freezer, and then heated, without ever suffering from either cold cracking or heat-related problems.
It is still yet further desirable to provide a reversibly collapsible container having any one or more of the above attributes which can be easily and inexpensively made, such as by thermoforming.
The objects of this invention include providing reversibly collapsible containers made from a polymeric material that can provide any or all of the above desired characteristics. These and other objects of the invention as hereinafter described may become apparent to one of ordinary skill in the art are intended to be encompassed by the present invention in accordance with the claims which follow.